Currently, as a non-aqueous electrolyte secondary battery for mobile devices such as cell-phone, lithium-ion secondary battery has been commercialized. In this non-aqueous electrolyte lithium-ion secondary battery, reduction in thickness of the battery itself has been required as reductions in weight and thickness of mobile devices progress. Recently, development of a thin type battery using a laminated film as an exterior material has progressed, and a laminate type of thin type battery using a lithium cobalt oxide (LiCoO2) as a positive electrode active material, a graphitic material or a carbonaceous material as a negative electrode active material, an organic solvent dissolving a lithium salt or a polymer electrolyte as a non-aqueous electrolyte is being put into practical use.
Furthermore, in recent years, along with shifts toward multifunction and high-performance of mobile devices, power consumptions of devices are increasing, and for battery as a power source for them, requirements of higher output power, high temperature stability in electrolytic solution, cost, and environmental issues are becoming more and more intensified. Consequently, development of lithium nickel composite oxides (for example, LiNiCoAlO2, Li(Ni,Co,Mn)O2), which can be expected to contribute to higher output power and improved high temperature stability in electrolytic solution in comparison with the existing lithium cobalt oxide, is progressing.
Aside from these applications, in recent years, in order to promote introduction of electric vehicle (EV), hybrid electric vehicle (HEV) and fuel cell vehicle (FCV) against a background of heightened environmental protection movement, developments of a power source for driving these motors or an auxiliary power source for hybrid electric vehicle, etc. are promoted. In these applications, a repeatedly chargeable and dischargeable non-aqueous electrolyte lithium-ion secondary battery is used. In an application such as driving a motor for EV, HEV and FCV where high output power and high energy density are required, since a single large type battery cannot practically be manufactured, an assembled battery, which is configured by plural batteries connected in series, is generally used. As a unit battery constituting such an assembled battery, use of a laminate type of thin type non-aqueous electrolyte lithium-ion battery (referred to simply as a thin type laminated battery) has been proposed (see, for example, JP-A-2003-151526).
Further, JP-A-2001-243951 discloses a positive electrode active material consisting of secondary particles, which are agglutinates of a number of primary particles, mentioning radial arrangement of said primary particles.
For more detail, a positive electrode active material for non-aqueous electrolyte secondary battery using lithium cobaltate, which consists of secondary particles that are agglutinates of a number of minute primary particles of lithium cabaltate represented by a general formula of LiCoO2, wherein said agglutinates of secondary particles have a number of minute vacancies into which electrolytic solution can penetrate and a tap density of 2.2 kg/cm3 or more, characterized in that at least a part of said minute primary particles are radially arranged along a direction from the center of secondary particle toward outside and that there are vacancies among a radially arranged minute primary particle and neighboring other similarly radially arranged minute primary particles, has been reported.